Abstract

A polarization study of Lyman-α radiation emitted in collisions of H+, H, He+, and He projectiles with H2 molecules has been performed at projectile energies ranging from 1–25 keV. In H+−H2 and H−H2 collisions, the measured linear polarization is negative at low incident velocities, indicating a preferred alignment of the excited electron charge cloud perpendicular to the incident projectile direction. This is taken as significance for a rotational coupling which in these two collision systems predominantly populates the H(2p±1) substates. In He+−H2 and He−H2 collisions, the measured linear polarization is about zero and independent of the projectile energy. In these more asymmetric systems,a′−a′ and a′−a″ couplings are now of comparable magnitude.